Lamp base



Feb. 18, 1947. P. o. CARTUN 2,415,867

LAMP BASE Filed Oct. 14, 1943 2 Sheets-Sheet 1 lnven'tor: PauL O. Car't'un,

His A*bcorne Feb.

Fig 8.

Filed Oct. 14, 1943 P. o. CARTUN LAMP BASE 2 Sheets-Sheet 2 Inven'tor: auL O. Carfim,

MM His A't'torney.

Patented Feb. 18, 1947 FICE LAMP BASE Paul O. Cartun, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation of New York Application October 14, 1943, Serial No. 506,230

Claims. (Cl. 17632) My invention relates, in general, to electric lamps and similar devices, and more particularly to a base or terminal structure for such devices and to methods and apparatus for the manufacture thereof. The invention is of especial utility in connection with electric discharge lamps of the well-known fluorescent type in general use at present, which usually comprise a tubular glass envelope having a base structure at each end thereof and a thermionic electrode sealed within each end of the envelope and electrically connected to the contacts or terminals of the adjacent base.

While the tubular envelope of fluorescent lamps of the type referred to above have usually been of circular cross section, it has been found that flattened glass tubes of more or less elliptical or oval cross section can also be utilized to advantage as envelopes for such type lamps.

One object of my invention is to provide a novel base or terminal structure for an electric lamp or similar device, and particularly for a lamp or device employing a tubular envelope of elliptical or flattened cross section.

Another object of my invention is to provide a base or terminal structure for electric lamps or similar devices of the double-ended tubular type, which base structure is characterized by high me chanical strength and possesses minimum dimensions longitudinally of the device whereby the latter is substantially unshaded from end to end.

Still another object of my invention is to provide a mechanically strong base or terminal structure for electric lamps or similar devices having tubular envelopes of elliptical or flattened cross section, which base structure conforms in contour to the cross sectional shape of the envelope.

A further object of my invention is to provide novel method and apparatus for manufacturing the base or terminal structure of an electric lamp or similar device.

A feature of the invention is the use of a flat metal member conforming in contour to the cross sectional shape of the envelope, which member is sealed by a fused seal to an end of the envelope and is provided with an exhaust opening as well as a pair of lead-in wire apertures through which lead-in wires extend to external metal contact elements or plates fused to glass beads or collars which are, in turn. fused to the flat metal member around the lead-in wire apertures therein.

Further objects and advantages of my invention will appear from the following description of species thereof and from the accompanying drawings in which:

Fig. 1 is a side view, partly in section, of a gaseous electric discharge lamp having a base or terminal structure of the type comprising my invention; Fig. 2 is a perspective view of an end of the lamp shown in Fig. 1; Fig. 3 is a perspective view of the terminal or mount structure for the lamp shown in Fig. 1; Figs. 4-9 are views showing the steps involved in making the base and terminal structure shown in Figs. 1-3 and in sealing the structure to the end of the lamp envelope; Fig. 10 is a sectional view showing the tipping off of the exhaust tube of the lamp comprising my invention; Fig. 11 is a section of a modified form of base or terminal structure comprising my invention; Figs. 12-14 are views showing certain of the steps involved in making the modified base structure of Fig. 11 according to one method; Fig. 15 is a view showing one of the steps involved in making the modified base structure of Fig. 11 according to another method; and Fig. 16 is a section of another modified form of base structure comprising my invention.

Referring to Fig. 1, the gaseous electric discharge device there shown comprises an elongated tubular glass container or envelope [0 having a base or terminal structure H sealed to each end thereof. The envelope ill may be either of circular, elliptical, or, as shown, flattened elliptical cross section, and contains a suitable ionizable gaseous atmosphere for providing an electrically conductive path in the envelope during the operation of the device. Preferably, the gaseous atmosphere within envelope l0 comprises a mixture of a rare starting gas such as argon at a pressure of a few millimeters, and a suitable metal vapor such as mercury vapor, for instance. A body l2 of mercury, which is vaporized during the operation of the device, may serve as the source of mercury vapor within envelope 10. Where the device is to serve as a fluorescent lamp, a coating l3 of a suitable fluorescent material may be applied to the inner surface of the envelope ill.

Each terminal structure ll comprises a base I 4 and anelectric energy translation element, such as an electrode l5, supported from the base by a pair of lead-in wires l6, I6, the ends of the electrode l5 being secured in a suitable manner, as by clamping or welding, to the inner portions of the lead-in wires 16. Each of the electrodes l5 preferably comprises a coiled-coil filament of tungsten having a coating of an electron-emissive material, such as barium oxide, thereon. The electrode coil l5 preferably is provided with a pair of auxiliary anodes ll preferably formed as extensions of the lead-in wires I6, the said extensions being suitably bent to form the anodes.

The base I4 according to the invention comprises a flat and relatively thin metal member or plate I8, such as sheet metal, conforming in contour to the cross sectional shape of the envelope I and sealed to the end of the envelope by a fused glass-to-metal seal. Where the envelope is of circular cross section, the metal base plate I8 may be in the form of a metal disc; but in the particular case illustrated wherein the envelope I0 is of flattened elliptical contour, the said base plate I8 is likewise of flattened elliptical contour. The metal base plate I8 consists of a metal or alloy which has a coefiicient of expansion approximating that of the glass of which the envelope is made and which seals readily thereto by fusion. For a soft glass such as the regular lime or lead glass commonly employed in electric lamp manufacture, the metal base plate I8 is preferably made of a chromeiron alloy such as that commonly known as Allegheny 55 and marketed by the Allegheny Steel Company.

The metal base or end plate I8 may be provided with an exhaust aperture I9 positioned at the bottom of a centrally located cup-shaped well or cavity 20 in the outer surface of the plate, The said exhaust aperture I9 is closed by the residue or tip 2| of an exhaust tube 22, the said tube being sealed by fusion to the base plate I8 over the exhaust aperture I9 therein and subsequently tipped off to form the tip 2| closing the said aperture I9. To protect the exhaust tube tip 2| from accidental breakage, the well 26 is made of sufficient depth to completely accommodate therein the exhaust tube tip 2| so that the latter will not project outwardly beyond the plane of the outer surface of the base plate I8.

The metal base plate I8 is provided with a' pair of spaced lead-in wire apertures 23 located at the bottoms of a pair of shallow cup or dishshaped depressions or sockets 24 formed in the outer surface of the base plate on opposite sides of the central cavity 20 thereof and preferably along the major axis of the base plate where the latter is of elliptical or flattened elliptical contour. The lead-in wires I6 extend through the apertures 23 and through glass insulator beads or buttons 25 which are received within the depressions 24 and are sealed, by a fused glass-to-metal seal, to the metal base plate I8 so as to hermetically close the said apertures 23. The lead-in wires I6 are embedded in the glass beads or buttons 25 and are thus supported and insulated from the metal base plate I8 by the said beads or buttons 25 which should be made of a glass which will readily wet and seal to the metal base plate I8.

As shown in Figs. 1 and 2, the glass beads 25 project a short distance, for instance inch or so, outwardly beyond the outer surface of the base plate I8 and have metal and contact elements or caps 26, preferably in the form of small metal discs substantially corresponding in diameter to the glass beads 25, fused to and covering the outer ends of the said beads. The contact discs 26 may be of either fiat or slightly rounded form (preferably the latter) with their convex sides outward as shown, and are made of a suitable metal to which the glass of the beads 25 will readily wet and fuse, such as the chromeiron alloy referred to above for instance. The

4 lead-in wires I6 are spot-welded or otherwise fastened at their outer ends to the metal contact discs 26 to thereby electrically connect the electrode coil I5 with the end contact discs 26.

Referring to Figs. 4-8 showing the steps involved in the manufacture of the base and terminal structure disclosed 'in Figs. 1-3, a pair of lead-in wire and terminal contact assemblies 21 of the type shown in Fig. 6 are first formed by spot-welding one end of a straight lead-in wire I6 to the inner concave surface 26 of an end contact disc 26 to form the unit 28 shown in Fig. 4. A glass collar 29 is then placed over the lead-in wire I6 so as to rest on the inner surface 26' of the contact disc 26, and the said collar, as well as the contact disc 26, heated by gas flames 30 until the glass softens and fuses to the inner surface of the contact disc 26 and flows down around the lead-in wire I6, thus completing the lead-in assembly 21 shown in Fig. 6.

The two lead-in assemblies 21, together with an exhaust tube 22, are then sealed to the base or end plate I8 to form the base assembly. In accordance with the invention, these sealing operations are preferably performed simultaneously and in the manner indicated in Fig. 7. As there shown, the base plate I8 is rested on top of a vertically arranged holder or support block 3| of a suitable refractory material, such as lava for instance. The base plate I8 is received within a recess 32 in the upper end of the holder 3|, the plate resting around its periphery on a ledge 33 within the recess. The side wall 34 of the recess 32, above the ledge 33 therein, conforms in shape to the contour of the base plate I8 so as to posi tion the said plate on the base holder. The base plate I8 is mounted in the recess 32 with the dish-shaped depressions 24 and cavity 20 thereof facing upwardly, a shOWIl. The lead-in wires I6 of the two lead-in assembliesZl are then threaded through the lead-in wire apertures 23 in the base plate I8 until the glass beads or buttons 25 rest against the base plate within the depressions 24 thereof. For this purpose, the refractory base holder 3| is provided with passageways 35 extending downwardly from the recess 32 and in alignment with the apertures 23 in the base plate to thereby accommodate the lead-in wires I6 and accurately center them in the base plate apertures 23. The exhaust tube 22 is supported by a spring-clip holder 36 in a position above the base plate I8 and in alignment with the exhaust aperture I9 therein, with the lower end of the tube resting against the bottom of the cavity 20 in the base plate. The exhaust tube holder 36 and the refractory base holder 3| may be supported on an upright post or standard 31 (Fig. 8) fastened to a table or frame 38, the exhaust tube holder 36 being mounted on the post so that it can be swung around thereon and locked in proper position to hold the exhaust tube 22 in alignment with the exhaust aperture I9 in the base plate.

With the base parts held in such assembled relation, the base plate I8 is then heated by induction to a very high degree to thereby cause the glass beads 25 and the exhaust tube 22 to be heated by conduction from the plate I8 and to be fused and sealed to the said plate. The inductive heating of the base plate I8 may be produced by a water-cooled coil 39 enclosing the upper end of the base holder 3| and connected to a suitable source 40 of high frequency current. The coil 39 may be suitably supported in place 2,41s,sev

5 around the holder 3|, as from the table 38 for instance.

During the sealing operation, a slight downward pressure i applied in a suitable manner to the contact discs 28 and the exhaust tube 22 to press the plastic glass down against the metal base plate I8 and insure a good seal therebetween. The contact discs 26 are pressed down to a predetermined height above the plane of the outer surface H of the base plate I8. For thi purpose, a suitable pressure-applying tool 42, having a tongue or extension 43 for engagement with the base plate I8, may be employed to press the contact discs 26 downwardly. as indicated in dashdot lines in Fig. 7.

While the above-described inductive method of heating the base plate I8 to effect the fusion of the glass bead 25 and the exhaust tube 22 to the said plate is preferred, such heating and sealing together of the base parts may be accomplished in any other suitable way. Thus, the base parts may be assembled in place in the relative positions shown in Fig. 7 on a suitable gas burner which direct gas fires against the metal base plate I8 to heat the same and fuse the glass of the beads 25 and exhaust tube 22 thereto.

After the lead-in assemblies 2! and the exhaust tube 22 have been thus sealed to the base plate I8, the lead-in wires I6 are then shaped to their final form and an electrode coil I5 mounted thereon to complete the mount structure 44 for the lamp, as shown in Fig. 3. The finished mount structure 44 i then secured to an end of the lamp envelope I to complete the end or terminal assembly of the lamp.

Referring to Figs. 8 and 9, the attachment of the mount structure 44 to the lamp envelope I0 is preferably accomplished by placing the mount structure on top the same refractory holder 3| previously used for sealing the base parts together. The mount structure 44 is mounted on the holder 3I with the base plate I8 received within the recess 32 of the holder in a position inverted from that hown in Fig. '7 so that the electrode I of the mount structure faces upwardly. To enable the mounting of the mount structure 44 on the holder 3| in such position, the said holder is provided with a centrally located vertical passageway 45 for the accommodation of the exhaust tube 22 therein while the recess 32 in the holder is made of sufiicient depth to likewise accommodate the metal-capped glass beads or buttons 25 of the mount structure. The open end of a vertically disposed envelope I0 is then placed over the lamp mount 44 with the end of the envelope resting on the base plate I8 and fitting within a small inturned peripheral flange or lip 46 with which the said plate is preferably provided. The envelope I0 is held in place in a pair of holders 4! each comprising a pair of spring-contracted pivoted jaws 48 mounted on the support post 31. The jaws 48 grip the envelope III to hold the same upright in alignment with the base plate I8 while permitting vertical sliding movement of the envelope therein. The metal base plate I8 i then highly heated by induction in the same manner as before (i. e., by the passage of a high frequency current through the coil 39) to cause the glass of the envelope to fuse and seal to the base plate I8. During the sealing operation, the envelope I II is preferably pressed downwardly against the base plate I8 by downward pressure suitably applied to the envelope, for example by a weight 48 mounted on, and vertically siidable in, an arm III fastened to the support post 31. When the glass of the envelope in contact with the heated base plate I8 becomes sufficiently plastic, the weight 49 moves the envelope down to thereby press the plastic glass into firm contact with the base plate, the downward movement of the envelope by the weight 49 being limited by the engagement of a stop shoulder 5| on the weight with the support arm 50 therefor.

To prevent the heated portion of the exhaust tube adjacent the base plate I8 from stretching during the envelope sealing operation under the influence of the weight of the tube itself, and thus closing the passageway through the said tube, suitable means are provided for holding up the exhaust tube 22 in fixed relation to the base plate -I8 during such sealing operation. Such tube holding means may consist, for instance, of three spring-pressed pins 52 extending radially through the holder 3|, at uniformly spaced points therearound, into the exhaust tube passageway 45 therein. The pins 52 have rounded inner ends for engagement with the exhaust tube 22, and they are pressed inwardly against the exhaust tube by plate springs 53 which are fastened at one end to the holder ill and bear at their other end against the outer ends of the pins.

In place of sealing the envelope I0 to the base plate I8 by inductive heating of the base plate, gas fires may be employed instead for such purpose, the mount 44 in such case being placed on a suitable gas burner which directs the gas fires against the peripheral portions of the base plate.

After the mount 44 has been sealed to one end of the envelope I0, the latter is inverted and another mount, similar to mount 44 but not having an exhaust tube 22 sealed to the bas plate I8 nor an exhaust aperture I9 in the said plate, then sealed to the other end of the envelope in the same manner as before. The envelope I0 is then evacuated through the exhaust tube 22 and current passed through the two electrodes I5 to activate them. The envelope Ill may then be filled with-a suitable gas, such as neon or argon at a pressure of, for instanceni mm. or so of mercury, and a small quantity of mercury I 2 or other vaporizable metal may also be added, after which the exhaust tube 22 is tipped off to thereby hermetically seal the envelope.

The tipping off of the exhaust tube 22 may be accomplished by the use of a tipping off head 54 of the form shown in Fig. 10 wherein the based end of the envelope I0 is positioned within a socket 55 in the head 54 and is held thereby in definite relation to fires 56 from a pair of gas burners 51 which extend from the head 54. The burners 51 direct the gas fires 55 at an angle into the central cavity 20 in the base plate I8 and against opposite sides of the exhaust tube 22 so as to close and seal the latter off at a point wholly within the cavity 28 and behind the outer surface 4| of the base plate I8.

The modified terminal structure. 58 illustrated in Fig. 11 is similar to that shown in Figs. 1-3 except that the base plate 59 thereof is not provided with the dish-shaped depressions 24 of the previous form and small ring-shaped glass beads are used in place of the button-shaped glass beads 25 to fasten the metal contact discs or caps 28 to the base plate. Unlike the glass beads 25 in the previous form of base construction, the glass beads 80 are not fused down around the lead-in wires I6, the said wires instead extending through the openings in the ring-shaped beads 68 to the metal caps or discs 25. Thus, the metal caps 28, as well as the-glass insulating beads 60,

7 form part of the end wall of the envelope itself, and hermetically close the lead-in wire apertures 23 in the base plate 59.

Referring to Figs. 12-14 illustrating one method of forming the modified terminal structure 58 of Fig. 11. a pair of lead-in assemblies 6| of the type shown in Fig. 13 are first formed by placing a glass ring 60 over the lead-in wire [6 of a lead-in wire and contact disc unit 28 of the type shown in Fig. 4, and resting the ring on the inner concave surface 26 of the end contact disc 26 of the said unit 28. The metal disc 26 and the glass ring 60 are then heated in a suitable manner, as by gas fires 62 directed against the outer convex surface of the disc and the lower end of the glass ring, to cause the said ring 60 to fuse and seal to the metal disc to form the lead-in assembly BI shown in Fig. 13. The two lead-in assemblies 6|, together with an exhaust tube 22, are then sealed to the base plate 59 by assembling the said parts in the same manner as shown in Fig. '7 and then heating the base plate'59 by suitable means to cause the glass rings 60 and the exhaust tube 22 to fuse and seal to the base plate. The sealing together of the base parts is preferably accomplished in the same manner as before, i. e., by mounting the base plate 59, the two lead-in assemblies El, and the exhaust tube 22 in place in the holders 3| and. 36, as shown in Fig. 14, and then passing a high frequency current through the coil 39 to heat the base plate 59 by induction. The remaining operations required for the completion of the modified terminal structu'p 58 are then exactly the same as before.

is an alternative method of forming the base assembly of the modified terminal structure 58, the fusion and sealing of the ring-shaped glass beads 60 to the metal discs or caps 26 may be performed simultaneously with the fusion and sealing of the said beads to the base plate 59. Thus the base plate 59, glass beads 60, lead-in wire and contact disc units 28, and exhaust tube 22 may be assembled in place in the manner shown in Fig. 15 and the base plate 59 and contact discs 26 then suitably heated to cause the 1 exhaust tube 22 to fuse and seal to the base plate and the glass beads 60 to fuse and seal to both the base plate and the contact discs. The heating of the base plate 59 to effect such sealing together of the base parts may be effectively accomplished by the same inductive method described hereinbefore in connection with Fig. '7, the base parts being mounted in place in the holders 3| and 36 as shown in Fig. 15, and a high frequency current then passed through the coil 39 to heat the base plate 59 by induction.

In the modified base structure shown in Fig. 16, the base plate 63 is provided with only one contact disc 26 instead of two such discs as in the previous forms of base construction. The contact disc 26 is located centrally of the base plate 63 and is fusion sealed to a glass bead 25 (or 60) which is also fusion sealed to the base plate ever a centrally located lead-in wire aperture 64 therein. A lead-in wire 65, fastened to the contact disc or cap 26, extends through the glass head 25 and the aperture 64 into the envelope l where it is connected to an electrode 66 which may be of the cold-starting hot-cathode type.

The base plate 63 may also be provided with an exhaust aperture 61 which is suitably closed, as by an exhaust tube tip 68, after evacuation and gas-filling of the envelope l0. Where the electrode 65 is of the hot-starting type requiring two lead-in wires, the other lead-in wire may be connected to the base plate 63 in which case the base plateitself serves as one of the contacts or terminals of the base structure.

The processes of manufacturing the terminal structure disclosed herein are claimed separately in divisional application Serial No, 652,327, filed March 6, 1946.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A double-ended electric lamp comprising a tubular glass envelope, a base and terminal structure at each end of said envelope comprising a substantially flat metal plate fusion sealed to the end of the envelope and serving as an end wall therefor, said plate having an aperture therein, a lead-in wire extending through said aperture and through a glass bead fusion sealed to the edges of said aperture, and a metal disc contact connected to said lead-in wire and fusion sealed to the said glass bead over the said aperture, said disc contact being spaced only slightly from said plate so that the base is of minimum depth.

2. A base for attachment to an end of a glass envelope for an electric device, said base comprising a thin metal member for sealing direct to the end of the envelope, said metal member having a pair of spaced lead-in wire apertures therein, a, pair of glass beads sealed directly to said metal member around the apertures therein, lead-in wires extending through said apertures and through said glass beads, and metal contact elements sealed directly to said glass beads and hermetically sealing the apertures in said metal member, said lead-in wires being connected to said contact elements.

3. A base for attachment to an end of a glass envelope for an electric device. said base comprising a thin metal plate for sealing direct to the end of the envelope, said metal plate conforming substantially in contour to the crosssectional shape of the envelope end and having a centrally located exhaust opening and a pair of lead-in wire apertures located on opposite sides of said exhaust opening, a pair of glass beads sealed directly to said metal plate around the lead-in'wire apertures therein, lead-in wires extending through said apertures and through said glass beads, and metal contact elements sealed directly to said glass beads and hermetically sealing the lead-in wire apertures in said metal plate, said lead-in wires being connected to said contact elements.

4. A base for attachment to an end of a tubular glass envelope of flattened elliptical cross-section, said base comprising a thin metal plate for sealing direct to the end of the envelope, said metal plate having a flattened elliptical contour eonforming to the cross-sectional shape of said envelope and having a pair of lead-in wire apertures spaced apart longitudinally of said metal plate, a pair of glass beads sealed directly to said metal plate around the apertures therein, lead-in Wires extending through said apertures and through said glass beads, and metal contact elements sealed directly to said glass beads and hermetically sealing the apertures in said metal plate, said lead-in wires being connected to said contact elements.

5. A base for attachment to an end of a glass envelope for an electric device, said base comprising a thin metal member for sealing direct to the end of the envelope, said metal member having a pair of spaced lead-in wire apertures therein, a pair of glass beads sealed directly to said metal member around the apertures therein and projecting outwardly from said member, a pair of lead-in wires extending through said apertures and said glass beads and embedded in the said beads, and metal caps sealed directly to the outer ends of said glass beads around the lead-in wires to thereby hermetically seal the apertures in said metal member, said lead-in wires being connected to said metal caps.

6. A base for attachment to an end of a glass envelope for an electric device, said base comprising a thin. metal member for sealing direct to the end of the envelope, said metal member having a pair of spaced lead-in wire apertures theme in, a pair of glass rings sealed directly to said metal member around the apertures thereof and projecting outwardly from said member, pair of lead-in wires extending through said apertures and through the openings in said glass rings, and metal caps sealed directly to and completely enclosing the outer ends of said glass rings to thereby hermetically seal the apertures in said metal member, said lead-in wires being connected to said metal caps.

7. A mount for sealing to an end oi a glass envelope for an electric device, said mount comprising a thin metal plate for sealing direct to the end oi the envelope, said metal plate conforming in contour to the cross-sectional shape oi the envelope end and having a centrally located cavity, an exhaust aperture at the bottom of said cavity, and a pair of lead-in wire apertures on opposite sides or said cavity, an exhaust tube having an end sealed directly to said metal plate within the said cavity and over the exhaust opening so as to be in communication with said opening, a pair of glass beads sealed directly to said metal plate around the lead-in wire apertures therein, a pair of lead-in wires extending through said apertures and through said glass beads, metal contact elements sealed directly to said glass beads and hermetically sealing the lead-in wire apertures in said metal plate, said lead-in wires being rigidly connected to said contact elements, and an electric energy translation element connected to said leading-in wires.

8. An electric device comprising a glass envelope having an electric energy translation element sealed therein and a terminal structure secured to an end thereof, said terminal structure comprising a thin metal member sealed directly to the said end of the envelope and having a' pair of spaced lead-in wire apertures therein, a pair of glass beads sealed directly to said metal member around the apertures therein and pro- Jecting outwardly of said member, metal contact elements sealed directly to the outer ends of said glass beads and apertures, and lead-in wires connected to said translation element and extending through the said apertures and glass beads and connected to said metal contact elements.

hermetically sealing the said 10 9. An electric device comprising a glass envelope having an electric energy translation element sealed therein and a terminal structure secured to an end thereof, said terminal structure comprising a thin metal member sealed directly to the said end of the envelope and having a pair of spaced lead-in wire apertures therein, a pair of glass beads sealed directly to said metal memher around the apertures therein and projecting outwardly of said member, metal caps sealed directly to and enclosing the outer ends oi said glass beads, and lead-in Wires connected to said translation element and extending through the said apertures and glass beads and connected to the said metal caps.

10. An electric device comprising a glass envelope having an electric energy translation element sealed therein and terminal; structure secured to an end thereof, said terminal structure comprising a thin metal member sealed directly to the said end of the envelope and having a centrally located cavity, an exhaust opening the bottom of said cavity, and a pair of lead-in Wire apertures on opposite sides of said cavity, said exhaust opening being hermetically sealed by an exhaust tube tip located entirely within the cavity and sealed directly to said metal mem-- her around the said opening therein, a pair of glass beads sealed directly to said metal member around the lead-in wire apertures therein and projecting outwardly of said member, metal c0ntact caps sealed directly to the outer ends of said glass beads and hermetically sealing the said lead-in wire apertures, and lead-in wire c0nnected to said translation element and extending through the said apertures and glass beads and connected to the said metal caps,

PAUL O. CAR'I'UN.

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